Well drilling bit



Feb. 19, 1957 A. 1. APPLETON WELL. DRILLING BIT 5 Sheets-Sheet 1 Filed Aug. 20, 1952 u INVENTOR.

Feb. 19, 1957 A. 1. APPLETON WELL DRILLING BIT 3 Sheets-Sheet 3 Filed Aug. 20, 1952 gixmwisdfl Egg... .1 l |OO\\Q IN V EN TOR.

arlhur 1 Clflole ton BY 4, W, 414% United States Patent 6 2,782,005 WELL DRILLING BIT Arthur I. Appleton, Northbrook, Ill.

Application August 20, 1952, Serial No. 305,464

6 Claims. (Cl. 255-340) The present invention relates in general to earth boring tools and, more specifically, to a novel rotary bit finding particular utility in the drilling of wells for oil, natural gas, or water.

As those skilled in the art are well aware, in rotary drilling a bit having hardened cutters is rigidly attached to a rotatable drill pipe by means of an intermediate fitting known as a drill collar. The drill pipe, collar, and bit are rotated in unison by a suitable prime mover located above the ground, such action causing the cutters on the bit to bite into the underlying earth formations. Mud-laden flushing fluid is pressurized and continuously circulated through the drill pipe and bit to the bottom of hole, returning to the surface outside of the drill pipe which is somewhat smaller in diameter than the gauge of the bit. The mud-laden fluid carries off the cuttings made by the drilling bit and also serves to wall up the hole. Drilling bits of different sizes and having various cutters for particular formations may be employed in this manner and will efiiciently bite through hard or soft underground formations.

Quite frequently, the drilling bit will encounter heaving shale or other caving formations as it progresses downwardly. If this should occur below but in the vicinity of a rock stratum through which the bit has previously passed, there is a possibility that, upon withdrawal of the bit, rock fragments and other debris will bridge or wedge around the drill pipe and across the exposed top of the bit head, thereby locking the bit against the underside of the rock stratum as the bit is raised in the hole. locking makes it impossible to withdraw the bit from the hole and may necessitate abandoning of the hole, resulting in substantial financial loss.

Accordingly, it is the general aim of the present invention to provide a rotary drilling bit capable of being freed with speed and facility in the event that it should become locked below a rock formation.

More specifically, it is an object of the invention to provide a sectional, rotary drilling bit susceptible of being collapsed, without loss of component parts, to free the bit from a locked condition and permit withdrawal of the same from the hole.

Another object is to provide a rotary drilling bit of the character set forth and having components susceptible of rigid assembly for normal drilling operation but also capable of ready detachment for shipment or replacement purposes.

A further object is to provide a drilling bit having the foregoing features, yet including adequate provision for circulation of flushing fluid therethrough.

Other objects and advantages will become apparent as the following detailed description proceeds, taken together with the accompanying drawings wherein:

Figure l is a front elevation of an illustrative drilling bit exemplifying the present invention.

Fig. 2 is an enlarged vertical sectional view taken axially Severe 2,782,005 Patented Feb. 19, 1957 through the drilling bit of Fig. 1 and in the plane of the line 2--2.

Fig. 3 is a perspective view showing one of the cutter holders per se which is included within the bit of Fig. 1.

Fig. 4 is an enlarged horizontal sectional view through the bit of Fig. 2 and looking upwardly, such view being taken in the plane of the line 4-4.

Fig. 5 is a plan view of the cutter holder illustrated in Fig. 3.

Fig. 6 is a perspective view showing the mandrel portion of the drilling bit of Fig. 1.

Figs. 7 and 8 are enlarged horizontal sectional views taken through the bit as shown in Fig. 2 and in the planes of the lines 7-7 and 8--8, respectively.

Figs. 9, 10 and 11 are sequential views illustrating the collapsing action of the drilling bit of Figs. 1 and 2.

While the invention is susceptible of various modifications and alternative constructions, a preferred embodiment has been shown in the drawings and will be described below in considerable detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings, the invention is there shown exemplified in an illustrative drilling bit 20 of the general type commonly employed for drilling through rock formations. The bit 20 in this instance comprises a sectionalized drill head 21 having three conical, toothed cutters 22 journaled thereon for rotation in a concave recess 24 (Figs. 1 and 2). The head 21 is surmounted by a hollow mandrel 25 which terminates at its upper end in a tapered shank 26, the latter being threaded for attachment to a drill pipe (not shown) by means of a drill collar 28.

When the bit 20 is placed with its cutters in contact with the ground or the bottom of a hole, and the drill pipe and drill collar 28 are rotated, all of these parts rotate in unison and in addition effect simultaneous rotation of the cutters 22 about their individual axes. The teeth of the cutters accordingly bite into the underlying ground formation and extend the hole downwardly. Pressurized, mud-laden flushing fluid is continuously supplied to the cutters 22 via a passage 29 in the shank 26 and an alined passage 30 in the mandrel 25 (Fig. 2).

Means are provided for collapsing the drilling bit 20 so as to permit ready withdrawal of the bit from the hole in the event that the bit becomes locked below a rock formation or some fixed obstruction as it is being raised in the hole. This is accomplished by utilizing a collapsible, sectionalized head structure in the bit, whereby individual head sections are rigidly held in unitarily assembled relation and retained by a means which becomes effective to release such sections in the event locking should occur during withdrawal of the bit.

Referring in particular to Figs. 1, 2 and 3, it will be perceived that the head 21 comprises a plurality of separate cutter holders 31 releasably secured in normal working position against the bottom of the mandrel 25. Each cutter holder 31 may be fashioned as a relatively heavy forging and in the present instance has a toothed, conical cutter 22 journaled thereon in a well-known manner. Each such cutter holder comprises an upper portion in the form of a slide 32 which snugly telescopes into a counterbore 34 adjoining the lower end of the mandrel 25, and also a lower portion in the form of a leg 35 projecting radially beyond the diameter of the mandrel and thence extending downwardly to support the cutter 22. The lower surface of the leg 35 may be generally concave and serves to define in part the concave cutter 3. QesaZsi. of. the drill. bit. Theupper surface of the leg comprises a flat seat 36 adapted to abut solidly against the bottom face 38 of the mandrel. The outer corners of the leg 35 adjoining; the seating surface 367 may be rounded off or chamfered as at 39.

To, provide a high. degreeof rigidity. and adequate strength for torque:transmissioniduringnormal operationof the drilling bit, the cutter holders 3h are permanently restrained: against turning or twisting movement relative to the mandrel 25. 1112 the present instance, this is accomplished lay-making, the cutter holder slides 32 in the form of complementary segments of a cylinder corresponding to the diameter of the mandrel couhterbore 34. In addition, the mandrel. ciounterbore' 3'45 is fashioned with; a series of; circumferentially spaced, longitudinally extending; cleats; 40, inthis case three, in. number. The cleats 40 have relativelyfiat reetangular exposed surfaces which; engage; corresponding keyway grooves 41 extending longitudinally of thecutter holder; slides 32. Aswill be evident from Figs. 3, 4,, 7- and 8, each slide 32 fits between an adjacent pair of cleats 40; in; muchthe-same manner as a machine tool carriage: fits its. supporting ways. Moreover, once a slide 32- has: entered the space between its associated cleats 41), it cannot be shifted. radially out of engagement therewith. This is a decided contribution to rigidity during normal; drilling operation and is an assetin assembling;thedrillingbit.

Although the cutter holder slides 32.completely. fill the counterbore 34 of the mandrel 25, suitable arrangements havebeen devisedfor insuring an adequate flow of fiushing fluid from the passages. 29. and; 30 to the cutters'22a To this end, each of the slide members. 32 has a longitudinal bore 42 communicating at; its.- upper end. withthe fluid. passage 30 of the, mandrel and at' its lower end with the concaye cutter recess 24.

In. order to maintain the cutterholder-s 31 and their associated cutters. 22in rigid, unitarily assembled, relation, releasable retaining means are; interposed betweenthe cutter holders 31 and mandrel 25. Inthis instance, such releasable retaining means comprises. a series; of frangible elementsin the form of shear pins 44. These pins, which-may be made of a number of materials such as soft steel or brass, are mounted radially of the mandrel 25in appropriate bores and each-pin projects radially into a corresponding one of the cutter holder slides 32, stopping short of; the flushingfluid passage42. The pins 44 may be tapered, threaded, on oriented somewhat differently from the arrangement shown in the drawing, thewill cause one or more of the pins 44 to shear. at theinner peripheral surface of the counterbore 34, thus permitting the slides 32 and cutter holders to separate from the mandrel'ZfSi andthe'reby, collapse the bit.

Provision is made for precluding loss of component parts when the bit 26 is collapsed after the manner just described, and without in any way impeding withdrawal of the collapsed bit. In furtherance of such objective, the respective cutter holders 3 are secured to the mandrel by means of normally inactive flexible connections, eachof a different length. In the present instance, each of thecutter holders 31 is'connected, as by meansof an eye 45 at its upper end; with a relatively sturdy check chain 46, the latter in turn being connected at its upper end with an eye 48 or some other appropriate anchor fitting fixed within the mandrel; 25. Each chain 46 is normally'housed within anindividual chain stowage compartment 49 housed within the mandrel 25 and situated over the'end ofits associatedslidefiz (Figs. 2, 4 and 7) In theillustrativebit 20, three such stowage compartments 49 are provided, being located in circumferentially spaced relation about the flushing fluid passage 30 but completely isolated therefrom. Shock absorber means, such as spring 47, may be interposed in each chain 49 or may be associated with its anchorage fittings 45, 48.

In order to facilitate replacement of cutters and cutter holders in the bit 20, as Well as ready detachment of such parts from the mandrel portion of the bit 25 for handling and shipment purposes, the flexible connections between the respective cutter holders 31 and the mandrel 25 include manually detachable elements. In this instance, each check chain 46 is equipped with such a detachable element in the form of a simple snap hook 50 which engages the eye 45' on the top of its associated cutter holder slide.

Turning now to Figs. 9, l0 and 11, the operation of the embodiment. of the invention described herein is shown: sequentially. Assume, at the outset, that the bit 20 is. being withdrawn from a hole 51 and that in the course of this maneuver the bit must be lifted past a caving formation 52 underlying a rock formation 54. As the;bit approaches the rock formation 54, rock fragments andiflother debris gather around the drill pipe 28 and eventually around the mandrel 25, ultimately bridging acrossthe upper surfaces of the bit head 21 and wedging between the latter and the underside of the rock formation; 55%, as shown in Fig. 9. This situation locks the bit against further upward movement. 7

Continued upward thrust exerted on the bit through the-drill: pipe and drill collar, along with the downward reaction, dueto the locking of the bit head in the hole, set up; stressesin the shear pins 44 which in this case aresuflicient to break them all. Accordingly, the mandrel zfg commences to pull away from the cutter holders 31 which define: the bit head 21, as shown in Fig. 10.

Once; the, foregoing, action occurs, the cutter holders 31 tend to separate vertically due to the combined action of gravity and the upward stresses applied to them sequentially as the slack is taken up in each of the check chains 46 This collapses the bit and yet permits orderly withdrawalof the cutter holders and cutters through the locked zone, as shown in Fig. 11.

Although it has been assumed for purposes of description'that. all three of the pins 44 sheared under the conditions just discussed, it should be appreciated that situations might arise where the locking action causes severance of a lesser number of pins and only partial collapse of thebit. Under such circumstances, a partial collapse of the bit should be sutficient to free it.

I claim as my invention:

1. An earth drilling bit of the rotary type and, comprising, in: combination, a hollow mandrel having means at. one end'forattachment to a drill collar, a plurality of cutter holders, a plurality of rotary cutters journaled upon corresponding ones of said cutter holders, each said cutter holder having a slide housed within said mandrel and a leg situated outside said mandrel but projecting radially beyond the same, said slides. being complementaryto each other and to the inside of said mandrel, means within said mandrel precluding movement of said slides relative thereto in all directions except one, a plurality offrangible 'elements securing each of said slides in dependently to said mandrel, said frangible elements when brokenpermitting movement of said slides in said one direction, and means mechanically connecting'said slides to said mandrelFf'or limiting the extent of movement of-said Slides in said one direction.

2. A rotarydrilling bit comprising, in combination, a hollow mandre1,a p1ur ality of cutter holders having cornplementa'ry surfaces which abutv each other when said.

holders relative to said mandrel, releasable means for,

securing each of said cutter holders to said mandrel, cut ters mounted on said outwardly extending portions of said cutter holders, said releasable means being releasable in response to a predetermined axial thrust on said laterally extending portion of said cutter holders in opposition to upward thrust on said drill bit to raise the latter, and means connecting each of said cutter holders to said mandrel for preventing complete disengagement thereof from said mandrel upon release of said releasable means.

3. A rotary drilling bit comprising, in combination, a plurality of cutter holders, means for holding said cutter holders together, each said cutter holder having a portion releasably attached to said holding means and another portion extending away from the same, a plurality of cutters mounted on said cutter holders, a plurality of releasable elements retaining said cutter holders and said holding means in rigidly attached condition, and a plurality of normally inactive flexible connectors coupled between respective ones of said cutter holders and said holding means to preclude loss of said cutter holders upon the release thereof from said holding means, each said connector being of different length from the other.

4. An earth boring drill bit of the rotary type and comprising, in combination, a hollow mandrel having means at one end for attachment to a drill collar, a plurality of cutter holders, each said holder having a slide housed within said mandrel and a leg situated outside said mandrel but projecting radially beyond the same, said slides being complementary and adapted to fill the inside of said mandrel, means defining a flushing fluid passage in said mandrel, means defining a flushing fluid passage in each said holder communicating with the passage of said mandrel, a plurality of rotary cutters journaled upon corresponding ones of said cutter holders, a plurality of frangible elements securing said slides to said mandrel and precluding withdrawal of said slides from the same, a plurality of flexible connections between said cutter holders and said mandrel, each said connection being of dilferent length from the other, and means defining stowage chambers within said mandrel for said flexible connections.

5. A rotary drilling bit comprising, in combination, a mandrel, a plurality of cutter holders, each said cutter holder having a portion slid-ably housed within said mandrel and another portion protruding radially and axially from the same, a plurality of cutters mounted on said cutter holders, means for releasably retaining said cutter holders and said mandrel in rigidly attached condition, flexible connections between said mandrel and said cutter holders permitting the latter to dangle below said mandrel upon actuation of said releasable retaining means, detachable coupling elements in said flexible connections, and shock absorber means operatively associated with each said flexible connection for cushioning the impact due to descent of the cutter holder.

6. An earth drilling bit of the rotary type and comprising the combination of a hollow mandrel having means at one end for attachment to a drill collar, a plurality of cutter holders, each said cutter holder having a slide housed within said mandrel and a leg situated outside said mandrel but projecting radially beyond the same, said slides being interlock-ed with the inside of said mandrel, means defining a flushing fluid passage in said mandrel, means defining a flushing fluid passage in each said holder communicating with the passage of said mandrel, a plurality of rotary cutters journaled upon corresponding' ones of said cutter holders, and a plurality of shear pins connecting said slides and said mandrel and precluding withdrawal of said slides from the same, a plurality of check chains disposed between said cutter holders and said mandrel, each said chain being of diiferent length from the other, means defining stowage chambers within said mandrel for said check chains, and snap hooks in said check chains.

References Cited in the file of this patent UNITED STATES PATENTS 1,326,509 Humason Dec. 30, 1919 2,049,543 Kammerer Aug. 4, 1936 2,208,457 Hurley July 16, 1940 2,318,370 Burch May 4, 1943 2,360,088 Walker Oct. 10, 1944 

